Mercury switch relay



Dec. 1, 1942. c. H. LARSON 2,303,371

MERCURY SWITCH RELAY Filed May 17, 1940 INVENTOR.

Y C a/z Jinx/ 507a ATTORNEYS Dec. 1, '1942. c. H. LARSON 2,303,371

MERCURY SWITCH RELAY Y Filed May 17, 1940 2 Sheets-Sheet 2 INVENTOR. Candi/imam? BY M 3 ATTORNEYS.

Patented Dec. 1, 1942 PATENT OFFICE 2,308,371 MERCURY SWITCH RELAY Carl B. Larson Ind., assignor to The Elkhart, Adlake Company, a corporation oi Illinois Application May 17, 1940, Serial No. 335,659

23 Claims.

in which switches having a glass envelope cannot be employed due to the possibility of breakage by excessive vibration or accidental blows.

.An important object of my invention is, therefore, to provide a shock resistant displacer type mercury switch formed of materials which may be readily shaped within close dimensional tolerances.

Other objects are to provide a switch having a high breakdown potential and low contact resistance capable of functioning as either a front or back contact switch, according to its position; to provide a displacer switch with a non-magnetic metal envelope having external means of adjusting an internal time delay; to provide a switch composed of sub-assemblies which are interchangeable with corresponding parts similar switches of like design; and to provide improved means of joining together these subassemblies.

Other objects and advantages will become apparent from the description and drawings, in which Fig. l is a vertical sectional view proved mercury switch positioned a front contact switch; I

Fig. 2 is a vertical sectional view of the same switch positioned o operate as a back contact switch;

Fig. 3 illustrates a modified form of my switch, incorporating a time delay element;

Fig. 4 is a diagrammatic view of an apparatus suitable for use in filling my switch with gas; and

Fig. 5 illustrates another form of my invention, incorporating a modified switch envelope;

Fig. 6 is a sectionalview of a reversible time delay element in an upright position; and

Fig. 7 is a sectional view of the same time delay element in an inverted position.

Referring to Fig. 1, the switch envelope II is of my imto operate as tubular in form, and has a uniiorn external 5 diameter. The interior friction, and counterbored at each at II, to form an internal shoulder ll.

combine with mercury,

close dimensional tolerances.

magnetic properties of these to be dueto the action of ple of such an alloy is stainless steel having an 01' 18 per cent chromium and 8 per cent nickel (generally termed 18-8 steel). I have found that this particular an envelope mateapproximate composition steel is well suited for use as rial, particularly as it is both placer may be held to the prevent the functioning velope may have undesirable effects.

A cap, generally designated l5, consists of a adapted to be received in the to fit snugly against the in- An opening is provided in is welded, or otherwise at- The thickness of the disk I6 is somewhat less than the depth when the disk I i metallic disk l6, counterbore l3 and ternal shoulders I. the disk It, to which tached, a small metal tube ll.-

is polished to decrease end, as shown The envelope consists of a non-magnetic metal which 5 will not amalgamate' or otherwise harmi'ully and which is capable 01' being machined or formed within reasonably envelope by the mag-- netic force employed to actuate the switch. As the functioning of the switch depends upon the of the switch, and as no air gap exists between the displacer and the envelope even a slight magnetic force in the enshoulders |l portions l3 of the envelope II will extend beyond the outer surface of the disk.

When it is desired to seal the cap ii to the switch envelope ii the cap is inserted, as described, against the internal shoulders i3, and the projecting portions I! of the envelope are turned inwardly against the exterior portion of the disk l3, thereby pressing the disk firmly against the shoulders I l. The joint between the turned-down portion l3 of the envelope H and the outer surface of the disk I6 is subsequently sealed with hard solder, as indicated at l3, or by other suitable material, to form a strong gastight joint. The disk may also be welded in place, if desired, and it may be of any suitable metal, as stainless steel, ordinary iron, or a metal known in the trade as Kovar.

A base 2| consists of a disk of metal adapted to be received in the counterbore |3, in a manner similar to that described in connection with the cap 15, and is provided with an opening 22 in which an electrode 23 may be positioned. The disk 2i is formed of a metal having a coefiicient of thermal expansion substantially equal to that of hard glass and molybdenum. A metal having these characteristics is commercially available under the trade name of Kovar, and consists essentially of an alloy of iron, cobalt and nickel.

The electrode 23 is preferably of molybdenum, and is covered for a portion of its length by insulating sleeve 23 or hard glass, such as Corning G405 AJ, which has a coefllclent of thermal expansion substantially equal to that of molybdenum and Kovar. The insulating sleeve 23 is preferably heat bonded to the electrode 23. The electrode 23 and the insulating sleeve 23 are positioned within the opening 22 in the base 2| by forming bulges or shoulders 23 in the insulating sleeve, adjacent to both sides of the opening 22, and subsequently applying sufilcient heat to cause the glass to bond to the base 2|. This forms a strong gas-tight seal, as the electrode, the glass and the base all have approximately the same coemcient of thermal expansion.

The insulating sleeve 23 surrounding the electrode 23 extends into the switch envelope H for slightly less than half the distance between the base 2| and the cap l5, and serves to insulate the electrode from contact with the base 2| and the mercury fill, except for a portion 21 of the electrode which extends beyond the insulating sleeve. The upper end of the sleeve 23 has a shoulder 23 formed integrally therewith, and fused to this shoulder is a ceramic tube 23, formed of a material, such as Alundum, which has substantially the same coeflicient of thermal expansion as the glass. The shoulder 23 is generally circular in section, but is formed eccentrically with respect to the electrode 23, so that the exposed portion 21 of the electrode will be close to one side of the ceramic tube 23 after assembly. The upper end of the ceramic tube 23 is closed with a glass seal 3|, and an opening 32 is provided through the side wall of the tube 23 approximately midway between the top and bottom thereof, and at a point furthermost removed from the eccentrically positioned electrode 23, The exposed portion 21 of the electrode 23 extends into the tube 29, and terminates adjacent to the glass seal 3|,

I prefer to form the entire electrode structure separately from the balance of the switch, and to seal this sub-assembly into the switch envelope in a manner similar to that described in eonnection with the cap I.

The displacer, generally designated 33, is telescoped over the electrode assembly, and may consist ot a tube 33 of magnetic material, such as iron, telescoped over a sleeve 33 of insulating material, such as glass, the latter sleeve being somewhat longer than the tube 33. The ends or the iron tube 33 are reduced in external diameter, forming an external shoulder 31. Guide washers l2 are fitted over the insulating sleeve 35 and the reduced portion 0! the iron tube 33 against the external shoulders 31, and may be of the type described in my Patent No. 2,060,811. These washers serve to prevent any sideward movement of the displacer assembly 33 by contact with the inner walls of the switch envelope Coil springs 33 are fitted over the projecting ends oi the interior insulating sleeve 33, and frictionally engage said sleeve to maintain the component parts of the displacer assembly 33 in their proper relation. These springs are oInon-magnetic material, and serve to prevent the sticking o! the displacer to either the cap I! or the base 2|, and are particularly necessary when the cap I5 is formed of a magnetic material, such as iron.

As the switch envelope serves as one o! the electrodes of the switch, it is often desirable, but not essential, to provide means of insulating the envelope H from other adjacent external portions or the switch assembly, and from accidental contact or short circuiting. This may be conveniently accomplished by mounting the assembled switch mechanism within a rigid tube 33, having a length somewhat greater than that o! the switch mechanism. The tube 33 may be suitably formed of an insulating material, such as Bakelite, and the switch assembly held within the tube by applying a suitable sealing material, such as sealing wax, to the ends or the tube after the switch mechanism is positioned therein, as indicated at 3|.

1! the switch assembly is to be mounted within an insulating tube, it is necessary to provide means of forming a connection with the electrodes, viz:--the switch envelope H and the centrally positioned electrode 23. This may be accomplished by attaching a connecting wire 32 to the switch envelope at any desired point, the wire being of suflicient length to extend beyond the tube 33. Electrode 23 may also be joined with a connecting wire in a similar manner, or

- extended beyond the tube. Connecting wires of this nature may be attached to the switch when the tube 33 is not employed.

A coil 43, having an iron circuit 33, is provided with an opening in which the switch assembly is positioned. Pole sleeves 36 may be provided litting around the tube 33 and in contact with the iron circuit 33 to define an air gap 31. If the coil is to be energized by an alternating current, the pole sleeves 4G, or the iron circuit 33, or both, may be split to overcome the undersirable magnetic effects of such current, as high eddy current or hysteresis loss. This split need not extend completely across the iron circuit, but may be positioned on the portions lying above and below the coil 43, extending from one edge of the iron circuit 33 to the opening in which the switch envelope is positioned. The split in the pole sleeves should be axial, and suflicient in' width to prevent contact of the edges of the sleeve when positioned around the switch. The magnetic portion 34 of the displacer 33 may also be split in a similar manner.

' The pole sleeves 49 are not essential, but are desirable, as they render the switch more sensitive to small exciting currents in the coil, and the action or the displacer 33 in response to the coil may be controlled within certain limits by adjusting the position of the air gap 41. The switch may be conveniently maintained in position within the coil 43 by means of a rubber sleeve 48, frictionally engaging the insulating tube 39, or the switch envelope II it the insulating tube is not employed. The sleeve 48 is cylindrical in form and has a central opening 01' a diameter slightly less than the external diameter of the tube 39 or the switch envelope II. The upper portion 01' the sleeve 48 is reduced in diameter to receive a bracket 49, of rigid material, which is adjustably secured to the iron circuit 44 by means of a machine screw 5|. The external diameter of the lower portion of the rubber sleeve 48 is greater than the diameter of the opening in the coil 43, so that the switch is prevented from moving downwardly by the frictional engagement of the sleeve 43 with the tube 39. Upward movement of the switch assembly is prevented by the bracket 49, which may also be used to deform the rubber sleeve 49 into firmer contact with the tube 39 or with the switch envelope ll,

. Other types of switch mountmay be adjusted.

The switch envelope it contains a quantity of mercury 52, and is filled with an inert gas, or mixture of such gases, belonging to the class comprising helium, hydrogen, nitrogen, argon, or helium hydride. The gas fill is admitted to the switch through the small tube I1 sealed to the disk IS, the opening of the tube I 1 communicating with the interior oi the switch. When the desired amount of gas has been admitted to the switch envelope the tube i1 is closed in a suitable manner, as by pinching and welding, indicated at 53. The gas fill may be of any desired pressure; either above or below that of the atmosphere, but I prefer to use relatively high preshigher break-down potential. In certain instances even higher pressures may be employed, as the efiiciency of the inert gas in quenching the arc increases with its pressure.

The displacer 33 floats on mercury fill 52 when the coil is deenergized, the amount of mercury in the envelope ll being such that when the displacer 33 is in its deenergized position the level 01' the mercury will be substantially half way between the base 2| and the cap l5. This is below the level which is termed the contact level oi! the electrode 21, that is, the level to which the mercury within the envelope must rise to complete the circuit. The opening 32 through the cup 29 determines the contact right, so that, when the displacer 33 is in its deenergized position there is no electrical contact between the electrode 23 and the switch envelope l I. The ceramic sleeve 29 forms a cup around the exposed portion 21 of the electrode 23, and in operation will always retain a certain amount of mercury in constant contact with the exposed portion of the electrode.

The air gap 41 is positioned somewhat below the displacer 33. When the coil is energized the displacer 33 is drawn downwardly, causing the mercury to rise within the envelope II and contact the pool-of mercury remaining within the sleeve 29 through the opening 32, thereby completing the circuit between the electrode 23 and the switch envelope ll. When the coil 43 is deenergized the displacer 33 will rise, due to its own buoyancy, causing the mercury level to fall within the envelope and break the contact between the electrode and the switch envelope.

The type of switch above described is generally known as a front contact switch, that is, a switch in which the circuit through the electrodes is normally incomplete when the controlling coil is deenergized. This is deenergized, and simply inverting the entire switch assembly. When the switch is inverted the parts will assume the positions shown in Fig. 2, wherein the mercury level, with the displacer 33 in its deenergized position, lies above the opening 32 in the ceramic sleeve 29, and the air gap 41 is positioned above the displacer 33. When the switch is in this position and the coil 43 is energized, the displacer 33 will be drawn upwardly, causing the mercury level to fall and break the contact between the electrode 23 and the switch envelope H through the opening 32.

Whether the switch is upright or inverted, the making or breaking of the circuit is always between mercury and mercury, for in the inverted position the ceramic sleeve 29 and the glass seal 3i also form a cup which retains a certain amount of mercury in constant contact with the exposed portion 21 of the electrode 23, regardless of the position of the displacer. The material from which the sleeve 29 is formed is also sufficiently porous to prevent entrapment of gas.

I have described in detail ing my switch to obtain a contact in either position.

It should be noted that the height of the mercury with respect to the base 2| in Fig. 1 is not necessarily the same as the height of the mercury with respect to the cap I 5 in Fig. 2, as the insulating electrode sleeve 24 and the electrode assembly displaces a certain amount of mercury. Therefore, unless correction is made, the normal height of the mercury within the switch envelope, when the switch is in its upright position, will be greater than when the switch is in its inverted position, as shown in Fig. 2. This level To provide a switch functioning as a back contact switch in either position, I may, for example,

-of the mercury will so that movement of enlarge the diameter of the opening 82 in the sleeve 29, so that in its upright position the level be above the lower margin of this opening. If necessary, I also increase the volume of the glass seal ll, so that in its inverted position the level or the mercury will also be above the opening 32. displacer 33, with respect to the air gap 41 is then altered by moving the switch envelope within the coil to a point where the air gap lies above the normal position of the displacer, so that when the coil 43 is energized the displacer 32 will be drawn upwardly, causing the level of the mercury to fall and break the normally existing electrical contact between the electrode 23 and the mercury illl 52. The switch will function in the same manner in the inverted position, the position of the switch within the coil being altered, however, in each case, so that the air gap l'l will be above the displacer.

My switch may be made to function as a front contact switch in either position by forming the opening 32 in the sleeve 25 at a point substantially half way between the cap l and the base 2i, and adjusting the mercury level to a point normally below this opening in either position. In this modification, the air gap must be positioned below the normal level of the displacer, the displacer in response downwardly, causing the and complete the fill 52 and the electo the coil 43 will be level of the mercury to rise contact between the mercury trode 23.

It may be seen, therefore, that by very minor adjustments I may obtain extreme flexibility in operation, and may provide a switch operating as a front contact when in one position and as a back contact when inverted, or as a front contact in either position, or as a back contact in either position. There are, of course, methods other than that described of controlling the operating characteristics, as the function of the switch depends upon the disposition of the opening 32 with respect to the mercury level. Broadly, if the switch is to function in the same manner, whether upright or inverted, the opening 32 should be substantially midway between the cap and the base, and the height of the mercury above the base in an upright position, substantially equal to the height of the mercury above the cap in an inverted poistion.

If, on the other hand, the switch is to function as a front contact switch in one position and as a back contact switch when inverted, the opening 32 will be positioned above the normal mercury level with the switch in one position, and below the normal level when inverted. In each case, it is understood that the direction and extent of movement of the displacer is such as to cause movement of the mercury tlll to change the condition of the circuit between the mercury and the electrode 23, and that the direction and extent of this movement may be controlled by changing the position of the switch envolope, and hence the displacer, with respect to the air gap 4'! in the iron circuit ll.

Due to the large area of the foot electrode or switch envelope H, the contact resistance of my switch is extremely low, thereby making it efficient to operate. The switch is also highly resistant to damage by accidental blows, and may therefore be used under circumstances which would prohibit the use of a switch having a glass envelope.

Fig. 3 illustrates a modified term of my inven- The position of the communicating envelope. A lateral opening I! is also provided a time delay element, generally designated 54. The envelope H is the same as that described in connection with Fig. 1, as is the base 2| and the lower portion of the electrode assembly. The cap, generally designated 6, is cylindrical in form, an outwardly extending end flange U, which is proportioned to be received in the counterbore IS in the end of the envelope H. The thickness of the flange i1 is somewhat less than the depth 0! the counterbore It, so that when the cap 58 is inserted in the end of the envelope it will fit tightly against the shoulder I4, and may be attached to the envelope in a manner similar to that described in connection with Fig. l. The cap 56 is providedwith' an axial opening II, with the interior oi the switch tion incorporating intercepting the axial opening 58, and proportioned to receive a tapered plug or stop cock ll containing a transverse opening '2, adapted to register, when in one position, with the opening 58, and when turned ninety degrees therefrom to close said opening. The upper portion of the cap is somewhat reduced in external diameter and is provided with external threads, as indicated at 82.

In this modification the insulating electrode sleeve 24 is formed with a larger external diameter, and extends upwardly to a point somewhat below the low mercury level, where the diameter of the insulating sleeve 24 is enlarged to form a shoulder 84, to which is fused a gas impervious thimble 26 of a material such as glass. The electrode 22 extends upwardly beyond the shoulder 84 within the thimble 66, and is insulated for a portion of its length by an extension 61 of the insulating sleeve 2i. This extension 81 also has a shoulder 68 formed upon its upper portion, to which a small ceramic sleeve 89 of Alundum, or other suitable ceramic material having a coefncient or thermal expansion substantially equal to that of the glass, is fused. This sleeve .69 fits around the exposed portion 21 o! the electrode 22, forming a cup in which a a small pool'of mercury is retained. If desired, the sides of this sleeve 69 may be truncated.

An opening 1| is provided in the side of the thimble 68, the diameter and position of the opening being such that the upper portion thereof is below the lip of the small ceramic cup 60. Another opening 12 is provided in the upper portion of the thimble 66, adapted to receive a plug 12 of porous material, through which gas may pass.

The displacer, in this instance, comprises a tube 14 of magnetic material, such as iron, having its external diameter reduced at each end to form an external shoulder 16. Guide washers l2 are fitted over the ends of the displacer and against the external shoulder 18. Portions of the tube ll extend beyond the shoulder 16 and the guide washers [2, which may be bent sharply outwardly, after the guide washers have been placed in position, to hold the washers in place, and then bent inwardly at an angle, forming legs 11, substantially as shown. These legs 11 serve to prevent any sticking of the displacer to the cap 50 or the base 2 i.

The coil 43 and the iron circuit 44 are similar to those described in connection with Fig. 1, but in place of the rigid tube 39 sleeves 1!, of insulating material, are interposed between the pole pieces 48 and the switch envelope H, to insulate the iron circuit 44. The switch may be supand is provided withcorporated in ported in the same manner as that previously decribed, with the rubber sleeve 48 in direct contact with the switch envelope I I.

Mercury is added to the envelope I I and the assembled switch connected with any suitable filling apparatus. In filling these switches with gas, particularly those incorporating a time delay element, I prefer to use an apparatus similar to that described in my. Patent No. 1,967,949, illustrated diagrammatically in Fig. 4. This apparatus may consist of a'pipe line 19, having a pressure gauge 88, a high frequency discharge device 8| connected to the pipe line through a valve 85, a three-way stop cock 82, a vacuum pump 83, and a source 84 of inert gas having a control valve 86. The gas supply 84 and the vacuum pump 88 are connected with the pipe line 18 through the stop cock 82. All parts of the system are preferably of metal with the exception of the extension 81, containing the electrode of the high frequency discharge device 8I, which is of glass.

Nipples 88, or other suitable connecting means,

this case, threaded to cooperate with the threaded portion 68 of the cap 56. When the switches have been attached to the pipe line 18, substantially as shown, the stop cock 6I in the cap 56 is turned to the open position, in which the transverse opening 62 registers with the axial opening 58, thereby allowing communication with the interior of the switch envelope. The stop cock 82 is turned to a position cutting oif the gas supply and connecting the pipe line 19 "with the vacuum pump 83. Air is exhausted from the inthe pipe line pump from the pipe line 19 and to connect the gas supply 84. The valve 86 is opened and gas is allowed to fill the switches.

This operation is repeated several times to insure the complete removal of all air, and in the final operation gas is admitted to the desired pressure and the stop cock 82 turned to a position disconnecting both the pump 83 and the gas supply 84 from the pipe line 19. The stop cock 6I inthe' valve cap 56 is turned to the oif position, thereby eifectively sealing the switch envelope II. If desired, switches may now be connected to a suitable testing circuit and their operating characteristics determined without removal from the filling apparatus.

It is, of course, obvious that the action of the time delay element will be governed largely by the pressure of the gas within the envelope II, and the time delay characteristics may, therefore, be conveniently varied by simply adjusting the gas pressure either while the switch envelope is after it s been removed. When the desired characteristics have been obtained, the switch is removed from the apparatus and the cap 56 dipped in hard solder, indicated at 89, completely covering the exposed portion of the cap 56.

The time delay element 54 is simply illustrative of one of the many types which may be inmy invention, and operates in the following manner: when the coil 43, surroundconnected to the filling apparatus or ing the switch, is energized the displacer 16 is drawn downwardly into the mercury, causing the mercury within the envelope II to rise rapidly until it reaches the upper limit 01' the ope 1|. The mercury outside 01' the thimble 66 will continue to rise rapidly, but as a certain amount of gas is trapped by the mercury within the thin:-

ble the rise of the mercury therein is delayed until a suillcient amount of the entrapped gas has escaped through the porous plug 18, allowing the mercury within the thimble 66 to rise to the lip of the interior ceramic cup 68 and comprete the circuit between the switch envelope II and the electrode 23. When the coil 48 is deenergized the displacer 14 will rise rapidly, due to its own buoyancy, causing the mercury outside fall. The mercury remaining within the tlumble, however, does not fall rapidly until the level of the mercury outside 0! also interchangeable with the cap 56 and the displacer 14 metal which may be readily dimensional tolerances.

The advantages accruing from this type of construction are obvious. For example, I may form several sub-assemblies, consisting of the ating characteristics. certain characteristics controlled, and testing may be eliminated except It would be impractical, from a manufacturing viewpoint, to form until the been obtained.

Fig. 5 illustrates particularly a modified torn;

of switch envelope II, in which the envelope is formed in the shape of an elongated cup. The counterbore I3 at the open end of this envelope,

as well as the internal and external diametersand the capacity, are the same as those previously described. An opening I is provided in the closed end of the envelope, to which the small tube I1, similar to that described in Fig. 1, may be attached. This tube may also be sealed in a similar manner. The remaining parts of the switch are similar to those described in Fig. 3, with the exception of the electrode structure, which is shown in its simplest form, comprising the insulating sleeve 24 having a shoulder 60 upon its upper end, to which is attached the small ceramic cup 69 surrounding the bared end of the electrode 23. The switch operates in a manner similar to that previously described.

This particular type of switch envelope possesses certain advantages, particularly in respect to the strength of the envelope, as it may be seen that one of the seals, viz: that formed between the cap and the envelope, is eliminated by this type of envelope. This feature is important in my switch, for, as previously mentioned, I prefer to use high gas pressures, and the envelope must, therefore, be sufllciently strong to safely retain the gas.

The time delay device 54, described in connec tion with Fig. 3, is, of course, adapted to operate only in an upright position. Figs. 6 and 7 illustrate a time delay element operable in either an upright or inverted position, and adapted for use in any one of the various modifications of my invention hereinbefore described.

Fig. 6 illustrates my reversible time delay element in its upright position. The element comprises a sleeve I02 of insulating material, such as glass or ceramic, attached to a shoulder IOI formed integrally with the insulating sleeve 20, and is closed at the top by a glass seal I03. The electrode 23 is positioned eccentrically with respect to the sleeve I02 and extends into said sleeve, terminating adjacent to the glass seal I03. The lower portion of the electrode within the sleeve I02 is insulated by an extension I00 of the insulating sleeve 24, the end portion of the electrode also being insulated by a cup I06 telescoped over the end of the electrode and heat bonded thereto, leaving exposed a centrally located contact I01.

Substantially identical mercury metering orifices I08 and I09 are provided in the wall of the sleeve I02, and are positioned above and below the level of the contact I01, the orifice I00 being adjacent to the shoulder MI, and the orifice I09 being adjacent to the glass seal I03. A relatively large opening III is also provided in the wall of the sleeve at approximately the level of the contact I01, all three of the above-mentioned openings being in the portion of the tube iurthermost removed from the eccentrically positioned electrode 23.

When properly positioned within the switch the level of the mercury, with the displacer In its deenergized position, will be approximately at the level indicated by the line A, below the level of the contact I01, and preferably above the mercury metering orifice I00. In this position there is, of course, no electrical connection between the mercury and the electrode 20. When the coil is energized the displacer is drawn downwardly, causing the level of the mercury outside of the sleeve I02 to rise rapidly. The rise of the mercury within the sleeve is, however, governed in this case by the size of the mercury metering orifice I00, and will therefore rise more slowly, eventually reaching the level of the mercury outside of the sleeve, indicated by the line B, in which position the mercury is in electrical connection with the contact I01. When the coil is deenergized the displacer rises, causing the mercury outside of the tube I02 to fall. This does not, however, break the contact between the electrode 23 and the mercury immediately, as the fall of the mercury within the sleeve I02 is delayed by the mercury metering orifice I00, through which the mercury slowly escapes.

Under the above described conditions it may be seen that this time delay element provides a delayed make and a delayed break, provided the high mercury level B is above the level of the contact I01 and below the lower margin of the relatively large opening II I. If desired, however, the Switch may be adjusted to provide a quick make with a delayed break by causing the mercury to rise to the level designated by the line C, in which the mercury will immediately fill the sleeve I02 through the opening III when the displacer is energized, completing the circuit between the contact I01 and the mercury. In this instance, when the displacer is deenergized, the mercury metering orifice I00 delays the tall of mercury within the sleeve I02 in a manner similar to that previously described.

The amount of mercury displaced by movements oi! the displacer depends, of course, upon the depth to which the displacer is drawn. and the high level of the mercury may, therefore, be adjusted by varying the position of the air gap between the pole sleeves with respect to the displacer. The mercury may, therefore, be made to rise to either. the level indicated by the line B, or that indicated by the line C, by adjusting the position of the switch within the coil; or, if desired, the high level of the mercury may be controlled by varying the amount of mercury added to the envelope.

Fig. 7 illustrates the time delay element shown in Fig. 6, in an inverted position. In this position there is normally electrical contact between the electrode 23 and the mercury when the displacer is in its deenergized position, the level of the mercury being normally at either the level indicated by the line D or that indicated by the line F. When the coil is energized the displacer is drawn upwardly, causing the mercury level outside of the sleeve I02 to fall rapidly. This action does not immediately break the electrical connection between the mercury and the contact I01, due to the action of the mercury metering orifice I09, which delays the passage of mercury out of the sleeve I02, thereby providing a delayed break. When the coil is deenergized the displacer falls to its normal position, causing the mercury level outside of the sleeve I02 to rise either to the level indicated by the line D or the level indicated by the line F. In the former case the mercury will immediately fill the sleeve I02 through the opening III, providing a quick make. It, on the other hand, the mercury rises only to the level indicated by the line F, the element will provide a delayed make, as the mercury will rise slowly within the sleeve I02, due to the action of the mercury metering orifice I09.

It is desirable that in all cases the mercury metering orifices I00 and I0! be normally below the low mercury level, for in this position the 7 surface tension eflect of the mercury does not switch is capable of operating on extremely low affect the flow through the orifice. If desired, exciting currents, and as it has very low contact By incorporating my reversible time delay eleand are strong and durable, thereby increasing ment any one switch may be made to function both the safety and durability of the switch. The in an upright position as a front contact switch high strength and unpermeability oi the metal having either a delayed make and a delayed switch envelope permits the advantageous useor break, or a, quick make and a delayed break. 10 a high pressure gas fill which cannot, of course,

and a delayed break. Any one switch incorpoto the switch envelope. rating the above described time delay element The joint formed between the switch envelope tinct types of action without alteration of any of pressures within the switch indefinitely, and is the component parts of the assembled switch. particularly eflicient in this respect when com- It will be noted that the construction 01' the pared to similar j in s in o h r types of switches reversible time delay element illustrated in Figs. employing rubber or other organic materials as 6 and 7 is, in many respects, similar to the eleca sealing medium,

trode cap described in connection with Figs. 1 The foregoing description has been by way of and 2. It is therefore possible, by adjusting the illustration only, and it is to be understood that diameter and position of the relatively large the specific embodiments herein described are opening ii I, the position of the air gap 41, merely examples of the many ways in which my before described operating as a front contact 3U to be construed as broadly as the prior art will switch in either position, the ad ustments being I claim as my invention: similar to those described in connection with 1 Inamercury switch,astationary switch on Fig, velope, a mercury fill, displacement means nor- Specifically', if it is desired to provide a switch mally at rest but actuatable toward one part of incorporating a time delay function, and operthe envelope for shifting the level of the mercury ating as a front contact switch in either posifill, and an electrode having a contact within th tion, the opening HI, corresponding to the openenvelope, the contact level of the electrode being ing 32 in Fig. 1, is positioned approximately above the mercury level when the envelope is midway W n he sw h envelope l and the 40 upright and below the mercury level when the level of the mercury adjusted to normally lie envelope is inverted, the actuation of said disbelow the level of the contact I01, as for explacement means toward id tt ample, the line designated A in Fig. 6, or at the velope causing the mercury to rise t t Contact level designated by the line E in Fig. 7. The level if the envelope is upright or to drop below switch envelope II is positioned with respect to the contact level if the envelope is in inv rt th air gap 41 to draw the displacer downwardly position, 7 into the mercury, causing the level of the mer- 2. In a mercury switch, a switch envelope, a cury to rise to the level indicated by the line B mercury fill, electrodes having contacts withi or the line C in Fig. 6, or to the level indicated the envelope, one of said contacts being adapted by the lines D or F in Fig. 7. to be intermittently placed in el t Contact The same switch may be made to function as with the mercury fill, a displacer having guides at back contact switch in either position by locatin contact with said envelope for shifting the ing the opening iii approximately midway withlevel of the mercury fill to change th condition in the envelope, and providing .a normal merof the circuit through th contacts, and means eury level at approximately the levels indicated for preventing movement of the switch envelope by the lines C or D in Fig. 6, or the lines D or F while shifting the level of the mercury fill, said in 7, If the switch is to function as a back switch being characterized by action as a front contact switch, the position of the air gap must contact switch in either an upright or an inalways be above the displacer, so that energizave t d positionti n f the coil 43 will cause the displacer to rise 3. In a mercury switch, a switch envelope, a out cf the mercury, thereby lowering th mermercury fill, electrodes having contacts within cury to a level such as that indicated by the line the envelope, one of' said contacts being adapted A i Fig, 6 or the line E in Fig. '7, these levels in to be intermittently placed in electrical contact both instances being below the level of the conwith the mercury fill, a displacer having guides tact I01. In either case, the displacement of in contact with said envelope for shifting the the electrode assembly and insulating sleeve 24 level of the mercury fill to change the condition may b compensated by increasing the volume of of the circuit through the contacts, and means the glass seal I03, or by other suitable means. for preventing movement of the switch envelope If, as previously described, the switch is to while shifting the level of the mercury fill, said operate as a front contact switch in one position, 7 switch being characterized by action as a back and as a back contact when inverted, the opencontact switch in either an upright or inverted ing I II is positioned to lie above the normal merposition.

cury level in one position, and below the mercury 4. In a mercury switch, a wit envelope, level when inverted. a mercury fill, contact means including an elec- Due to its simple and efficient construction, my trode extending into the switch envelope, .said

8. electrode being covered for a portion of its length by 'an insulating sleeve defining a contact below the normal mercury level when the switch envelope is in one position and above the normal mercury level when the switch envelope is inverted, means effective in both positions of the envelope for shifting the level of the mercury fill to bridge and unbridge the contact means, and means for preventing movement of the switch envelope while shifting the level of the mercury fill.

5. In a mercury switch, a switch envelope, a mercury fill, contact means including an electrode extendin into the envelope and covered for a portion of its length by an insulating sleeve, said sleeve defining a contact adapted to be intermittently immersed by the mercury fill, the relationship between the mercury fill and the contact being such that said contact is above the normal mercury level when the switch is in one vertical position and below the normal mercury level when the switch is inverted, a ceramic body telescoped over said contact and adapted to retain a quantity of mercury in continuous contact with said contact for substantially any position of the switch envelope, and a magnetically responsive plunger for shifting the level of the mercury fill.

6. In a mercury switch, a switch envelope, a mercury fill, contact means includingan electrode extending into the envelope and covered for a portion of its length by an insulating sleeve, said sleeve defining a contact adapted to be intermittently immersed by the mercury fill, a ceramic body telescoped over said contact and adapted to retain aquantity of mercury in continuous contact with said contact in substantially any position of the switch envelope, and a magnetically responsive displacer for shifting the level of the mercury fill, the relationship between the height of the mercury fill and said contact being such that movement of the displacer afi'ects the condition of the circuit through the electrodes in the same manner whether the switch envelope is upright or inverted 7. In a mercury switch, a stationary switch envelope, a mercury fill, contact means including an electrode projecting into the envelope and covered for a portion of its length by an insulating sleeve, said sleeve defining a contact normally immersed in the mercury fill whether said switch is upright or inverted, and means for shifting the mercury fill away from said contact, said switch being characterized by action as a back contact switch in either an upright or an inverted position.

8. In a mercury switch, a stationary switch envelope, a mercury fill, contact means including an electrode projecting into the envelope and covered for a portion of its length by an insulating sleeve, said sleeve defining a contact normally above the level of the mercury fill whether said switch envelope is upright or inverted, and means for shifting the level of the mercury fill to a point above said contact, said switch being characterized by action as a front contact switch in either an upright or inverted position.

9. In a displacer type mercury switch, a switch envelope, a mercury fill, contact means within the envelope including an electrode partially covered by an insulating sleeve, said sleeve defining a contact adapted to be intermittently immersed by the mercury fill, a movable mercury displacer, and immovable means within the envelope adapted to displace a predetermined portion of its length by an amount. of mercury to equalize the space above and below said contact whereby the position of the normal mercury level with respect to said intermittently immersed contact does not vary when the switch is inverted.

10. In a displacer type mercury switch, a switch envelope, a mercury fill, contact means within the envelope including an electrode partially covered by an insulating sleeve, said sleeve defining a contact adapted to be intermittently immersed by the mercury fill, and means within the switch envelope adapted to displace a predetermined amount of mercury whereby when the switch envelope is inverted the normal level of the mercury fill may be fixed with respect to said intermittently immersed contact.

11. In a displacer type mercury switch, a switch envelope, a mercury fill, contact means including an electrode extending into,the envelope, an insulating sleeve telescoped over said electrode and defining a contact adapted to be intermittently immersed in the mercury fill, and a mercury retaining thimble of insulating material inclosing said contact and secured at its base to the upper end of the insulating sleeve, said mercury retaining thimble having a side wall opening below the end of the contact and above the upper end of the insulating sleeve.

12. In a displacer type mercury switch, a switch envelope, a mercury fill, contact means including an electrode extending into the envelope, an insulating sleeve telescoped over said electrode and defining a contact, a tube 01' ceramic material telescoped over said contact and secured at its base to the upper end of the insulating sleeve, the upper end of said ceramic tube being closed, said tube having a side wall opening below the end of the contact and above the upper end of the insulating sleeve whereby mercury is retained in continuous contact with said electrode for substantially all positions of the switch.

13. In a mercury switch, a switch envelope, a mercuryfill, contact means including an electrode projecting into the envelope and covered for a insulating sleeve, said sleeve defining a contact adapted to be intermittently immersed by the mercury fill, means for shifting the level of the mercury fill. and means for delaying movement of the mercury fill with respect to said intermittently immersed contact, said delay means being operable when the switch is upright or inverted.

14. In a mercury switch, a switch envelope, a mercury fill, contact means including an electrode projecting into the envelope and covered for a portion of its length by an insulating sleeve, said sleeve defining a contact adapted to be intermittently immersed by the mercury fill, means for shifting the level of the mercury fill, and an insulating sleeve telescoped over said intermittently immersed contact and closed at one end, said sleeve having mercury metering orifices above and below the level of said contact whereby movement of the mercury with respect to said contact may be delayed when the switch is operated in either an upright or inverted position.

15. In a mercury switch relay, a coil. an iron circuit associated with the coil and defining an air gap, a switch envelope associated with the iron circuit, a mercury fill, contact means including an electrode projecting into the envelope and covered for a portion of its length by an insulating sleeve, said sleeve defining a contact adapted to be intermittently immersed in the mercury fill, a magnetically responsive displacer adapted to shift the level of the mercury fill, a time delay body telescoped over said intermittently immersed contact and having mercury metering orifices above and below the level of said contact, said time delay body also having a relatively large opening at the level of said contact, and means controlling the height of the high mercury level whereby said switch may be selectively operated as a slow make, slow break switch or a fast make, slow break switch, regardless of whether the switch is operated in an upright or inverted position.

16. In a mercury switch, a sub-assembly com prising an electrode, an insulating sleeve telescoped over said electrode and defining a contact, and a time delay body telescoped over said con tact, said body being closed at its upper end and secured at its base to said insulating sleeve, said body having mercury metering orifices above and below the level of the contact.

17. For use in a displacer type mercury switch, a reversible time delay element adapted to enclose a contact, said element comprising a cupshaped ceramic body having mercury metering orifices in a side wall adjacent to each extremity.

18. For use in a displacer type mercury switch, a reversible time delay element adapted to enclose a contact, said element comprising a cup-shaped ceramic body having mercury metering orifices in a side wall adjacent to each extremity and a relatively large side wall opening intermediately positioned with respect to said mercury metering orifices. l

19. In a displacer type mercury switch, a switch envelope, a mercury fill, a contacting means within the envelope adapted to be intermittently immersed by the mercury fill, opposed mercury retaining pockets around said contact defining an opening between said pockets at the level of said contact, said mercury retaining pockets being immovable with respect to the contact whereby mercury is retained around the contact whether the envelope is upright or inverted.

20. In a mercury switch, a switch envelope, a mercury fill, contact means including an elec-- trode projecting into the envelope and covered for a portion of its length by an insulating sleeve, said sleeve defining a contact adapted to be intermittently immersed by the mercury fill and positioned above the normal level of the mercury fill whether the switch is upright or inverted, means for shifting the level of the mercury fill, and means for delaying movement of the mercury fill with respect to said intermittently immersed contact, said time the switch is upright or inverted, the switch being characterized by action as a front contact time delay means being operable when t delay switch in either upright or inverted position.

21. In a mercury switch, a switch envelope, a mercury fill, contact means including an electrode projecting into the envelope and covered for a portion of its length by an insulating sleeve, said sleeve defining a contact adapted to be intermittently immersed by the mercury fill, the level of said contact being above the normal level of the mercury fill when the switch is upright and below the normal level of the mercury fill when the switch is inverted, means for shifting the level of the mercury fill, and means for delaying the movement of the mercury fill with respect to said intermittently immersed contact, said delay means being operable when the switch is upright or inverted, the switch being characterized by action as a front contact time delay switch when upright, and a back contact time delay switch when inverted,

22. In a mercury switch, a switch envelope, a mercury fill, contact means including an electrode projecting into the envelope and covered for a portion of its length by an insulatin sleeve, said sleeve defining a contact adapted to be intermittently immersed by the mercury fill, the level of said contact being below the normal level of the mercury fill when the switch is upright or inverted, means for shifting the level of the mercury fill, and means for delaying movement of the mercury fill with respect to said intermittently immersed contact, said delay means being operable when the switch is upright or inverted, said switch being characterized by action as a back contact time relay switch in an upright or inverted position.

23. In a mercury switch relay, a coil, an iron circuit associated with the coil and defining an air gap, a switch envelope adjacent the iron circuit, a mercury fill, contact means including an electrode projecting into the envelope and covered for a portion of its length by a sleeve, said sleeve defining a contact adapted to be intermittently immersed in the mercury fill, a magnetically responsive displacer adapted to shift the level of the mercury fill, a time delay body telescoped over said intermittently immersed contact and having mercury metering orifices above and below the level of said contact, said time delay body also having a relatively large opening intermediate said orifices and above the high level of the mercury fill when the switch is upright, but below the high level of the mercury fill when the switch is inverted whereby said switch may be operated as a slow make, slow break when upright, and as a fast make, slow break switch when inverted.

CARL H. LARSON. 

